Circuit breakers are one of a variety of overcurrent protection devices used for circuit protection and isolation. The circuit breaker provides electrical protection whenever an electric abnormality occurs. In a typical circuit breaker, current enters the system from a power line and passes through a line conductor to a stationary contact fixed on the line conductor, then to a movable contact. The movable contact is fixedly attached to a pivoting arm. As long as the stationary and movable contacts are in physical contact, current passes from the stationary contact to the movable contact and out of the circuit breaker to down-stream electrical devices.
In the event of an overcurrent condition (e.g., a short circuit), extremely high electromagnetic forces can be generated. The electromagnetic forces repel the movable contact away from the stationary contact. Because the movable contact is fixedly attached to the rotating arm, the arm pivots and physically separates the stationary and movable contacts, thus tripping the circuit. Upon separation of the contacts and blowing open the circuit, an arcing condition occurs. The breaker's trip unit will trip the breaker which will cause the contacts to separate.
In the past, as shown in FIG. 1, circuit breakers have used handle bearings that cooperate with the moving arm 25. The handle 15 pivots and the arm 25 rotates between “OFF”, “ON” and “TRIP” positions. During endurance testing per UL 489, the arm 25 is rapidly repetitively moved through its operative positions. The moving arm 25 may wear into the handle or the handle may undesirably degrade, e.g., exhibit blistering due to one or more of heat, friction and/or forces from the arm.